Are reusable rockets the future of space flight?

A photo from SpaceX shows the first stage of a Falcon rocket that landed on a platform in the Atlantic off the Florida coast in early May after launching a Japanese communications satellite.

Photo: Associated Press

Like a lit candlestick tossed toward the ground, the 135-foot rocket arced toward a tiny platform, barely distinguishable as it bobbed on a hazy blue sea. Countless thousands of eyes were trained on the long metal tube with its bright yellow flame and four carbon-fiber legs, so apparently fragile.

To the untrained observer, it seemed to be coming in a little too fast. Would it slow down in time? Would the legs hold?

Yes. And yes.

When the engines cut off on that day in early April and the Falcon 9 remained upright, a glass-shaking roar went up around SpaceX headquarters in California, outside Kennedy Space Center in Florida and throughout much of the space-loving world.

It was a moment — the moment — that company founder Elon Musk had been predicting, promising and praying for as his engineers kept trying to work through the challenge of sending the first stage of a rocket into space and then flying it back again for a proper landing.

Returning the rocket and controlling its landing instead of letting it splash into the ocean is at the heart of SpaceX’s core mission, captured in a quote from Musk on the company’s website: “A fully reusable vehicle ... is the fundamental breakthrough needed to revolutionize access to space.” With reusability comes lower cost, he points out, and that means everything.

With SpaceX having proved that a rocket booster can be returned to land or sea, that time would appear to be at hand. Or is it?

For all the deserved praise over the technical accomplishment, the voice of skeptics can still be heard amid the media hosannas. Bringing the rocket back is a big thing, they say, but only one thing. Making sure it can quickly be sent back up, at no great expense and with no higher likelihood of failure than when it was brand-spanking new, is something else entirely.

In much of the popular press, the ability of SpaceX to return its first stage with an upright ocean landing was all but tantamount to proving Musk’s vision. A first soft landing had come on a launch pad, an impressive achievement but of limited practical value. The second successful landing on the downrange vessel, about the size of a football field, was the real breakthrough.

Fortune Magazine trumpeted that “space just got a whole lot cheaper.” Its article asserted that the path forward was now set, thanks to SpaceX and Blue Origin, a launch company that had also returned its first stages with controlled landings, albeit after suborbital flight. “Costly, expendable space rockets are on their way out,” the magazine asserted, and with them the high cost of reaching space.

The billionaire Musk, a native of South Africa who made his money in other ventures, clearly was the man of the hour.

“I think it’s another step toward the stars,” Musk said at a news conference after the April 8 launch and landing. “In order for us to really open up access to space, we’ve got to achieve full and rapid reusability. And to be able to do that for the primary rocket booster is going to (have) a huge impact on cost.”

That SpaceX did it again a month later, landing another Falcon 9 on a drone ship after a more demanding launch, was but one more confirmation. Three times in a row his company has done what once was considered improbable.

“May need to increase size of rocket storage hangar,” Musk joked via Twitter after the third rocket was brought back to land.

But another tweet by Musk recently drew less attention.

“Most recent rocket took max damage, due to high entry velocity” he wrote.

And therein lies the rub. There was no obvious damage to the rocket as it stood on the floating pad, but inside the machine, where the nine Merlin engines reside, it was a different story.

The rocket that had, along with its second stage, powered a Japanese communications satellite into a higher geostationary orbit, then amazingly landed far downrange on the tiny SpaceX drone ship, would not be reused, Musk said. Instead, it would be used as a test bed of sorts to see how well it could still function in its damaged state.

Dan Dumbacher, an engineering professor at Purdue University, understood as well as any what that rocket had been through. A NASA veteran for 35 years, he served as a top executive in the Human Exploration and Operations directorate at agency headquarters and had overseen the space shuttle’s return-to-flight operations.

“The part everyone likes to forget is this: When you are dealing with high-performance engines, you are running close to the margins,” said Dumbacher, whose long résumé includes stints working with experimental reusable vehicle projects. “Going from zero to 17,000 miles an hour is not a trivial pursuit. We are trying to do something that is very hard, and in a very harsh environment.”

Dumbacher said the stresses placed on rocket engines and other parts during a powerful ascent mean that every piece has to be subjected to rigorous scrutiny upon return. And that takes a large investment of time and technology, he said. A seemingly small item that gets a cursory look could end up having devastating consequences.

“Our failures are buried down in the deep details,” Dumbacher said.

Originally, the space shuttle was intended to be reflown with minimal refurbishment and refitting. But that did not occur. The demands placed on the shuttle engines during launch were so intense that they had to be removed upon return and painstakingly overhauled. Eventually, the time between flight readiness was reduced, and a number of the important engine parts were reused on many flights.

“The shuttle was a different vehicle for a different application than a Falcon 9 is,” said Dumbacher, who is hopeful that the latter has greater reuse potential. “This is a less technically complex machine than what we used on the shuttle. It’s not trying to do as complex a job as the shuttle main engine was doing. The simpler and less complex the task, the more the chance of reusability.”

Dumbacher said SpaceX, over time, should be able to improve its rocket and minimize the refurbishment needed. Whether it makes economic sense to do so is another matter, he said.

“One or two flights doesn’t demonstrate the viability of the concept,” he said.

How close SpaceX might be to its goal of “rapid reuse” is unknown. The secretive company did not respond to requests for comment and typically does not allow its engineers or executives to speak to the media. Nor does Musk often grant interviews, limiting his media availability to launches.

Competing launch companies also are not buying into the notion of reuse — rapid or otherwise — of the intact first stages of their rockets, except for suborbital operations such as Blue Origin, for which it is all but required. The reasons are simple. Flying it back places performance limits on the rocket, including the weight of fuel that must be reserved for a controlled descent. The required second ignition of the engine puts even more wear and tear on an already stressed machine, as does the landing procedure. How much true reuse will take place is unknown.

Ultimately, no matter how stunning the image of a rocket landing on a drone platform may be, only the market will determine whether it makes sense. European rocket launcher Arianespace said reusability does not figure into its business model. Similarly, NASA launch contractors Orbital ATK and United Launch Alliance are not jumping on board, although the latter has a reuse concept of its own that involves separating the engines and bringing them back to earth in a protective envelope.

“I applaud their technological achievements,” said George Sowers, vice president for advanced programs at ULA and a longtime rocket engineer. “Obviously, as a rocket guy, I think that’s really cool and impressive. The economic viability is much more problematic than the technological viability. That’s far from being proved.”